Single frame advance mechanism for movie projectors

ABSTRACT

An improved intermittent film transport for a motion picture projector includes a film claw adapted to periodically engage and advance a film strip and a single frame advance mechanism for restraining the film claw from engaging the film until the mechanism is selectively actuated by the operator. When actuated, the mechanism is effective to release the film claw and permit it to advance the film by a single image frame before the claw is again intercepted and restrained.

Oct. 9, 1973 United States Patent [19] Thomson [5 1 SINGLE FRAME ADVANCEMECHANISM 1,943,303 1/1934 Foster............................. 352/169 XFOR MOVIE PROJECTORS Inventor ayes [75 Kenneth William Thomson,

Rochester, N.Y.

m .le m0. m d m mm Wa mm C Tr C m Al fi Rfia Tt s n Bmd Anm C mm mr .mmm e J m mo. mm iu 7 d UAW k a 2 mw K mi mh let M w ER m d A F I 3 2 7 2l l odically engage and advance a film strip and a single ining the filmechanism is selectively actuated by the operator. When [21] App]. No.:288,446

frame advance mechanism for restra claw from engaging the film until them [52] U S Cl 352/169, 352/191 actuated, the [51] Int. G03b 21/38mechanism is effective to release the film claw and 352/137, 169, 168,permit it to advance the film by a single image frame before the claw isagain intercepted and restrained.

[58] Field of Search...................

6 Claims, 3 Drawing Figures References Cited UNITED STATES PATENTS3,533,688 Painton................ 352/137 X PAIENTED UB1 9 I976 SHEET18F Z SINGLE FRAME ADVANCE MECHANISM FOR MOVIE PROJECTORS CROSSREFERENCE TO RELATED APPLICATION Reference is made to commonly assignedcopending U.S. Pat. application Ser. No. 250,263 entitled, TWO FRAMESPER SECOND DEFEAT MECHANISM filed May 4, 1972 in the name of J. J.Bundschuh.

BACKGROUND OF THE INVENTION 1. Field Of The Invention This inventionrelates generally to web handling apparatus such as a motion pictureprojector which has a film claw driven to engage and advance a filmstrip, and more particularly to a single frame advance mechanism forcausing the film claw in a motion picture projector to engage andadvance the film strip by a single image frame each time the mechanismis actuated.

2. Description Of The Prior Art An improved slow motion projectionmechanism has been described in commonly assigned U.S. Pat. ApplicationSer. No. 250,263 entitled, TWO FRAMES PER SECOND DEFEAT MECHANISM" filedMay 4, I972 in the name of J. J. Bundschuh wherein the film claw of themechanism can be periodically restrained from engaging and advancing areceived film strip. Such a defeat mechanism is suitable to provide veryslow projection speeds (e.g., 2 frames per second), but in certaininstances it is desirable to provide for stop frame projection and topermit the operator to selectively advance a film by a single frame topermit viewing of greater detail. While known mechanisms are suitable toprovide stop frame viewing, the defeat mechanism disclosed in theBundschuh application is especially suitable for use with the improvedsingle frame advance mechanism of the present invention.

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved motion picture projector mechanism for effecting stop frameprojection.

It is another object of the present invention to provide an improvedfilm claw control mechanism for a motion picture projector which permitsthe film claw to engage and advance a film strip at a normal rate (e.g.,18 or 24 frames per second) or, alternatively, by a single image frame.

It is a further object of the present invention to provide an improvedmotion picture projector mechanism BRIEF DESCRIPTION OF THE DRAWINGS Inthe detailed description of the preferred embodiments of the inventionpresented below, reference is made to the accompanying drawings inwhich:

FIG. I is a perspective view, partially exploded, of a preferredembodiment ofa single frame advance mechanism according to the inventionwhich is adapted to cooperate with the transport mechanism of a motionpicture projector;

FIG. 2 is a side view of the embodiment shown in FIG. 1 showing inphantom the movement of the control linkage of the invention whichcauses advancement of the film by a single image frame; and

FIG. 3 is a side view of the embodiment shown in FIG. 1 showing theprojector mechanism in an operative position and the single frameadvance mechanism in position to disable the film claw of the projector.

for causing a film claw to engage a film stripto selectively advance thefilm by a single image frame.

According to a preferred embodiment of the invention, an improved filmtransport mechanism for a motion picture projector includes a mechanismfor selectively restraining the film claw from being driven into contactwith the film strip. The single frame advance mechanism prevents thefilm claw from being driven by the in-and-out cam of the projector untilthe operator actuates a manual control, thereby permitting the operatorto selectively advance the film to permit stop frame viewing.

The invention and its objects and advantages will become more apparentfrom the detailed description of the preferred embodiment of theinvention presented below.

DESCRIPTION OF THE PREFERRED EMBODIMENT Because photographic apparatusare well known, the present description will be directed in particularto elements forming part of, or cooperating more directly with, thepresent invention, apparatus not specifically shown or described hereinbeing understood to be selectable from those known in the art.

The embodiment of the present invention shown in the accompanyingdrawings and discussed herein is especially suitable for use with theprojector embodiments disclosed in detail in the afore-mentioned,commonly-assigned copending U.S. Pat. application Ser. No. 250,263 filedin the name of J. J. Bundschuh wherein a slow motion defeat mechanism isprovided for a motion picture projector having a single film claw forone type of film or having two film claws which are selectively operablefor either super 8 or regular 8 mo tion picture films.

Referring now to the drawings, FIGS. 1 through 3 show a projectormechanism 20 which includes claw arms 22 and 24, each having pairs ofclaw teeth 22a and 24a respectively, for engaging different film types.Claw arms 22 and 24 are mounted to move up and down and also to pivot inand out relative to the film gate (not shown) of the projector by use ofany suitable pivot arrangement, as for example, the ball and racestructure 26 which is described in detail in commonlyassigned U.S. Pat.No. 3,402,006 entitled, MOTION PICTURE PROJECTOR issued in the name ofJ. J. Bundschuh et al. on Sept. l7, I968, the disclosure of which isincorporated herein by this reference. Claw arms 22 and 24 are bothnormally urged in a counterclockwise direction about pivot 26 by biasingmembers (not shown) such that the claw teeth 22a and 240 are urgedtoward the film strip whenever in-and-out cam followers 28 and 30 passinto indentations on the face of a cam 42 as will be described in detaillater.

The up-and-down movement of the claw arms 22 and 24 is under the controlof up-and-down or pull-down cams 32 and 34 respectively, which aresecured to a drive shaft 40 and are embraced by follower surfaces 36 and38 of claw arms 22 and 24 respectively. As is well known, eachrevolution of up-and-down' cams 32 and 34 is effective to produce onecomplete reciprocal stroke of film claws 22 and 24. Thus, as describedin the aforementioned Bundschuh et al. U.S. Pat. No. 3,402,006 whereshaft 40 is typically driven at 54 revolutions per second, claws 22 and24 are both caused to reciprocate in the up-and-down or film advancingdirection at a rate of 54 strokes per second.

At the same time that the claws 22 and 24 are reciprocally driven in thefilm advancing direction, one of the claws can be selectively driven inand out or'in the film engaging and disengaging direction while a filmselector lever or film slide 52 effectively restrains the other clawfrom engaging the film in a manner which will be described in greaterdetail later. The unrestrained claw is driven by a cam mechanism whichis also well known. A radial or face cam 42 is secured to a shaft 44which is rotatably mounted in the projector substantially parallel withthe drive shaft 40 and is driven in synchronism therewith by knownmeans, such as a gear drive. As best shown in FIG. 1, the face cam 42 isprovided with a plurality of groups of depressions or indentations 46,46' (and others not shown) which have various radial dimensions and arespaced circumferentially about the face of cam 42. As described incommonly assigned US. Pat. No. 3,261,654 issued in the name of Faber etal. on July 19, I966, these indentations cooperate with cam followers 28and 30 to cause the pairs of claw teeth 22a and 24a respectively, to bemoved into and out of engagement with a film strip at variousfrequencies so as to achieve various predetermined projection speeds,such as 54, I8 and 6 frames per second.

As best seen in FIG. 1, film slide 52 is slidably mounted on theprojector housing in any suitable manner such as by rivets 51 which passthrough an elongate slot 53 in the slide and are secured to theprojector. A

shaft 54 is secured to slide 52 for moving control arms 56 and 58 asslide 52 is moved. Control arms 56 and 58 are both pivotably mountedabout shaft 44 and are resiliently urged into contact with the shaft 54by springs 60 and 62 respectively.

Extending from control arm '56 is a stud shaft 64 which is engageablewith tab portion 68 of the film claw 24. Stud shaft 68 is effective todrive claw 24 in a clockwise direction about the pivot 26 and holdingthe claw from moving in the film engaging direction whenever slide 52 ispositioned at the R8 position for regular 8 operation. (FIG. 1position). Similarly, a stud shaft 66 extends from control arm 58 forcontacting tab 70 of film claw 22 and for preventing the claw arm 22from engaging the film strip when slide 52 is moved to the right to theindicates S8 or super 8 position. Movement of slide 52 from the regular8 to the super 8 position would also allow spring 60 to urge control arm56 in a counterclockwise direction about shaft 44 thereby removing studshaft 64 from contact with tab 68 and allowing film claw 24 to resumebeing driven for engaging and advancing film in response to in-and-outcam follower 30.

The projector mechanism shown in FIGS. 1 through 3 also includes a speedor speed slide 50 which may be moved to any of several predeterminedlocations before or during operation of the projector to determine theprojection speed. As is well known in the motion picture art, movementof slide 50 causes cam followers 28 and 30 to be shifted and positionedalong the face of in-and-out cam 42 such that the cam followers are inalignment with different ones of the groups of depressions 46, 46'. Asface cam 42 is rotated, the claw arm which is unrestrained is then urgedto follow the inward movements of cam follower 28 or 30 as previ- 4 lously explained. The resulting inand-out motion of the claw arm allowsthe film to be engaged and advanced as the claw is also being movedup-and-down in synchronous relation by the up-and-down cam.

To provide projection speeds which correspond to less than oneadvancement of the film per revolution of cam 42, the projectormechanism shown in FIGS. 1 through 3 includes a defeat mechanism of thetype which is fully disclosed in the aforementioned Bundschuhapplication, but will now be briefly discussed to aid in understandingof the embodiment of the present invention.

As best shown in FIG. 1, a pinion 72 is secured to a shaft 44 adjacentto slide member 50. Pinion 72 drives a gear 74 which is secured to shaft76 and since pinion 72 has one-third as many teeth as gear 74, gear 74and shaft 76 are necessarily driven at onethird the speed of shaft 44.Thus, where shaft 44 is typically driven at a speed of 6 revolutions persecond, shaft 76 is driven at 2 revolutions per second.

A ratchet member 78 is secured to shaft 76 closely adjacent to gear 74and could be integral therewith. A cam 80 is rotatably mounted aboutshaft 76 in a position closely adjacent to ratchet member 78.Eccentrically secured to the inner surface of cam 80 is a pivot shaft 82which extends over the outermost surface of ratchet member 78. A pawl 84is pivotally mounted on shaft 82 between cam 80 and gear 74. Pawl 84includes a first end portion 86 which is positionable for engagingratchet member 78 and a second end portion 88 which is positionable forcontacting a bent-off tab portion 90 of slide member 50 as will beexplained in greater detail.

A spring 92 urges pawl 84 in a counterclockwise direction about shaft 82such that end portion 86 is brought into engagement with ratchetmember78 whenever slide 50 is positioned to the positions shown in FIGS. 1through 3 wherein end portion 88 does not contact tab portion 90 ofslide 50. That is, when slide 50 is positioned for single frameoperation, as shown in FIGS. 2 and 3, or two frames per secondoperation, as shown in FIG. 1, end portion 88 can no longer contact tab90 and spring 92 then urges pawl 84 to pivot about shaft 82 until theend 86 of pawl 84 is operatively engaged with ratchet 78. When pawl 84is thus engaged with ratchet 78, the cam 80 is effectively coupledthrough pawl 84 to shaft 86 and caused to rotate as if it were itselfsecured to shaft 76. That is, the rotational force applied to ratchet 78is transmitted by pawl 84 to shaft 82 which in turn causes cam 80 to bedriven by shaft 76 as if those members were a single unit being drivenat 2 revolutions per second in the preferred embodiment. Spring 92 iseffective to hold pawl 84 into engagement with ratchet 78 until slidemember 50 is again moved to the left for operation at 54, 18 or 6 framesper second whereupon tab 90 once again is brought into contact with endportion 88 causing pawl 84 to be held disengaged from ratchet 78.

A'plate 96 which is bifurcated at one end to form extensions 96a and96b, is slidably secured to the projector by a rivet 98 and is mountedabout shaft 76 which passes through an elongated opening 100 in theplate. Secured to the central portion of plate 96 is a shaft 94 which ismaintained in contact with surface 81 of cam 80 by a spring 102 which issecured to both the plate and the projector in any known manner.

As disclosed in the aforementioned Bundschuh application, shaft 94 iseffective to follow the contour of cam surface 81 as cam 80 is rotatedand to overcome the force of spring 102 to drive plate 96 to the left asshown in FIGS. 3. When plate 96 is moved to this position, extensions96a and 96b are in contact with stud shafts 64 and 66 causing the clawarms 22 and 24 to be restrained by the engagement of these shafts withtabs 68 and 70. Cam surface 81 is effective to hold plate 96 in thisposition for approximately 240 of rotation and thereby restrain the clawarms 22 and 24. As the cam 80 continues to rotate, shaft 94 continues tofollow along the contour of camsurface 81 and passes into an indentedportion thereof, as seen in FIG. 3, allowing spring 102 to again movethe plate 96 to the right and allowing extensions 96a and 96b to beremoved from contact with stud shafts 64 and 66 approximately 80 ofrotation of cam 80. The effect of movement of stud shafts 64 and 66 intoand out of contact with the tabs 68 and 70 once per revolution of cam 80is to allow the unrestrained film claw to follow the movement of thein-and-out cam follower only once for every third revolution of thein-and-out cam 42. That is, for every six revolutions of in-and-out facecam 42, cam 80 rotates twice and allows a film claw to be urged by itscam follower into engagement with the film only twice. Thus, this defeatmechanism is effective to provide advancement of the film at a rate oftwo frames per second.

The projector mechanism shown in the drawings also includes a preferredembodiment of a single frame advance mechanism for cooperating with thepreviously discussed defeat mechanism to permit the film claws 22 and 24to engage and advance the film only by a single image frame each time acontrol mechanism is selec- -tively actuated. The embodiment of thepresent invention cooperates with the defeat mechanism of the projectorto selectively disengage pawl 84 from'ratchet 78 and cause extensions96a and 96b to be held in position for restraining film claws 22 and 24until the advance mechanism is operated in a manner which will behereinafter described. While the advance mechanism shown and describedherein is manually controlled, it will be understood by those skilled inthe art that such a mechanism could readily be controlled by othermeans, such as an electric solenoid or electric motor.

As best shown in FIG. 1, a catch 110 is pivotally secured to the speedslide 50 by any known means such as a rivet 114. Catch 110 is normallyurged in a counterclockwise direction about rivet 114 and into contactwith pin 115 by a spring 116 which bears against an edge of catch 110and against a post 118 .which is also secured to the slide 50. As isshown in FIG. 2, when catch 110 is held in contact with pin 115 andspeed slide 50 is set for single frame operation, end portion 112 of thecatch is positioned to be engageable with end portion 88 of pawl 84 asthe cam 80 and the pawl 84 are rotated. As catch 110 is contacted by endportion 88, it is effective to cause pawl 84 to become disengaged fromratchet 78 and thereby prevent cam 80 from being driven. When pawl 84 isdisengaged in this manner, cam 80 is stopped in a position wherein shaft94 remains in contact with that portion of cam surface 81 which is notindented so as to maintain end portions 96a, 96b of plate 96 in contactwith stud shafts 66 and 68, thereby restraining claw arms 22 and 24 fromengaging and advancing the film. Thus, cam surface 81 holds plate 96 inposition to permit viewing of the single image frame of the film untilcatch is caused to release pawl 84 and cam 80 is again rotated in amanner to be hereinafter described.

A bracket 120 is pivotally and slidably mounted on the projector byknown means such as the rivet 128 which is secured to a projectorthrough the elongated opening 122 of bracket 120. A peg 130 is securedto the projector and passes through a generally rectangular opening 124in bracket 120 which is positioned near the end of the bracket 120opposed to slot 122, and which is thereby effective to limit the travelof bracket 120. As will be explained later in greater detail, bracket120 is movable in response to movement of both a toggle 138 and the camsurface 81 to cause a single frame of film to be advanced.

A toggle 138 is pivotally mounted to the projector by a pin 146 whichextends through an elongated opening 142 such that the toggle is readilyaccessible by the operator and is manually movable. Toggle 138 isnormally urged in a clockwise direction about pin 146 by a spring 144and is held in the FIG. 1 position until it is manually caused to pivotagainst the force of the spring 144.

One end of a rod 134 is secured to toggle 138 and the other end of therod is secured to bent off portion 120a of bracket 120. Although in theembodiment shown, threaded fasteners 136 and are screwed upon thethreaded ends of rod 134 to provide adjustment of the travel of bracket120 and toggle 138, other known fastening means could also be used.Also, it would be possible to substitute a cable or other flexiblemembers for rod 134 if appropriate fasteners are used and if bracket 120is urged to the right by appropriate spring means.

Referring now in particular to FIGS. 2 and 3, the operation of thesingle frame mechanism will now be described. As shown in these figures,slide 50 has been moved to the single frame position as indicated by thealignment of the indicator mark on slide 50 with the letter S on theprojector. When slide 50 is in this position, the cam followers 28 and30 are positoned upon the face of cam 40 such that they may contact onlya single indentation as cam 40 is rotated. Thus, where cam 40 is drivenat 6 revolutions per second, the cam followers would cause either one ofthe film claws 22m 24 to engage and advance the film at a rate of 6frames per second. However, as shown in FIG. 2, when pawl 84 isdisengaged from ratchet 78 by catch 110, extensions 96a and 96b contactstud shafts 64 and 66 and drive them under tabs 68 and 70 of the filmclaws wherein the film claws 22 and 24 are restrained from engaging thefilm until plate 96 is again moved to the right, thereby permittingviewing of a single image frame.

When the projector mechanism is in the FIG. 2 position, bracket 120 iscaused to pivot about in the clockwise direction about rivet 128 untilsurface [20c of bracket 120 is in contact with the portion of camsurface 81 which is indented. Thus, when toggle 138 is manually pivotedto the left, as shown in phantom, bracket 120 is also moved to the leftby rod 134. As end 120b of bracket 120 is brought into contact withcatch 110, the catch is moved in a clockwise direction about rivet 114until end 88 of pawl 84 is released. Spring 92 causes pawl 84 to pivotabout post 82 until end 86 is again engaged with ratchet 78.

Once ratchet'78 is engaged by pawl 84, cam 80 is caused to rotate againand, as shown in FIG. 3, post 94 contacts the indented portion of camsurface 81 permitting spring 132 to urge plate 96 to the right. As plate96 is moved to the right in this manner, extensions 96a and 96b arewithdrawn from contact with stud shafts 64 and 66 so as to permit theunrestrained claw arm to engage and advance the film strip by a singleimage frame. The continued rotation of cam 80 from the FIG. 2 positioncauses bracket 120 to be pivoted in a counterclockwise direction aboutrivet 128 as surface 120C is contacted by the enlarged portion of camsurface 81 and the force of spring 132 is overcome. As a result,

end lb of bracket 120 is pivoted away from catch 110 and the catch isthen pivoted by spring H6 back into contact with pin 115 wherein it isin position (FIG. 3) to once again engage pawl 84. Thus, even if theoperator holds the toggle 138 to the left instead of pulsing the toggleas normally would be done for single frame operation, the stop framemechanism automatically limits the projector mechanism to advancing asingle frame. Of course, as soon as the operator releases the toggle138, the bracket 120 will again be moved to the FIG. 2 position and inthis position is ready to be again operated to cause a single frame tobe advanced.

If the operator desires to operate the projector at a speed other thanthe single frame operation, simply moving speed slide 50 to a positionother than that shown in FIG. 2 and 3 causes pawl 110 to be moved fromposition for end [12 thereof to contact end 88 of pawl 84 and normaloperation of the projector can be resumed.

The invention has been described in detail with particular reference toa preferred embodiment thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

1 claim:

1. In a film transport mechanism having a film claw adapted tointermittently engage and advance a film strip having a plurality offilm frames, first cam means adapted to drive said claw to engage andrelease said film strip, second cam means, ratchet means rotatable aboutan axis, pawl means coupled to the second cam means and movable into andout of engagement with said ratchet means for driving said second cammeans synchronously with said first cam means when the pawl means andratchet means are engaged, restraining means operatively coupled to thesecond cam means and positionable relative to the claw by said secondcam means into and out of a position for periodically holding said clawineffective to engage said film strip, the improvement comprising:

' means for disengaging the pawl means from the ratchet means when thesecond cam means has p0.- sitioned the restraining means in its positionfor holding the claw ineffective to engage the film strip, therebyeffecting prolonged projection of a single frame, said disengaging meanscomprising a catch mounted for movement between (1) a first positionwherein the catch is located with respect to the pawl to disengage thepawl from the ratchet and (2) a second position wherein the catch isdisengaged from the pawl, and said disengaging means further comprisesmeans for moving the catch between its first and second positions.

2. In a film transport mechanism having a film claw adapted to engageand advance a film strip, first cam means adapted to drive said claw toengage and release said film strip, second cam means, ratchet meansrotatable about an axis pawl means movable into and out of engagementwith said ratchet means for driving said second cam means synchronouslywith said first cam means when the pawl means and ratchet means areengaged, restraining means operatively coupled to the second cam meansand positionable relative to the claw by said second cam means into andout ofa position for periodically holding said claw ineffective toengage said film strip, the improvement comprising:

disengaging means shiftable between (1) a first condition wherein saiddisengaging means is effective to disengage said pawl from said ratchetmeans, thereby permitting said restraining means to be held by saidsecond cam means in the position wherein said claw is ineffective toengage said film strip and (2) a second condition wherein saiddisengaging means is ineffective to disengage said pawl and ratchetmeans; and

a shift means coupled to said disengaging means and effective to shiftsaid disengaging means between its first condition and its secondcondition.

3. The improvement as set forth in claim 2 further comprising:

cycle control means controlled by the second cam and cooperating withsaid disengaging means in response to movement of the shift means toeffect shifting of the disengaging means from its first condition to itssecond condition, said cycle control means permitting the return of thedisengaging means to its first condition from its second condition afteradvancement of a single film frame and following movement of the firstcontrol means to a position for moving the disengaging means to itssecond condition, whereby said film strip is engaged and advanced onlyone frame each time said disengaging means is selectively shifted fromits second to its first condition. I

4. For a motion picture projector or the like, a transport mechanismadapted to selectively advance a motion picture film for stop frameviewing of a single frame of film, said mechanism comprising:

a. first means for periodically advancing said film at a first rate,said means comprising a film claw adapted to be synchronously moved intoand out of engagement with said film and to advance said film by asingle frame when said film claw is engaged with said film;

b. second means adapted to periodically restrain said first means fromadvancing said film, thereby effecting advancement of film at ase'condrate, said second means comprising cam means operable synchronously withsaid film claw and a ratchet and pawl coupled to the'cam means forcontrolling operation of the cam means, the ratchet and pawl beingadapted to be shifted between (1 a first condition wherein said pawl isdisengaged from said ratchet so that said ratchet and pawl are therebyineffective to operate said cam means; and (2) a second conditionwherein said pawl is engaged with said ratchet so that said ratchet andpawl are effective to cause said cam means to be operated synchronouswith said film claw, and restraining means operable by said cam meansfor restraining said film claw from movement into engagement with saidfilm;

c. a member adapted to engage said pawl to change said ratchet and pawlfrom said second condition to said first condition; and

d. means for selectively moving said member between (l) a first positionwherein said member is engageable with said pawl and (2) a secondposition wherein said member is removed a spaced distance from saidpawl.

5. In a motion picture projector having a film claw adapted to engageand advance a strip of film, first means to drive said claw into and outof engagement with the film during advancement of an increment of film,second means adapted to restrain said claw from being driven intoengagement with the film by said first means, said second meansselectively movable between (1 a first position wherein said secondmeans is effective to restrain said claw, and (2) a second positionwherein said second means is ineffective to restrain said claw, theimprovement comprising:

a. toggle means movably secured to a first portion of said projector;

b. bracket means movably secured to a second portion of said projector;

c. connecting means for connecting said toggle means and said bracketmeans such that movement of said toggle means produces movement of saidbracket means;

(1. catch means for selectively cooperating with said second means tomove said second means from said first position to said second position,said catch means being located with respect to said bracket means sothat the catch means is controlled by said bracket means in response tomovement of said toggle means; and

e. means for returning said second means from said second position tosaid first position after said claw has engaged and advanced anincrement of film.

6. In a motion picture projector as set forth in claim 5 wherein saidreturning means comprises cam means which cooperate with said bracketmeans to move said bracket means from (1) a first position wherein saidbracket is ineffective to cooperate with said catch means to (2) asecond position wherein said bracket is effective to cooperate with saidcatch means.

1. In a film transport mechanism having a film claw adapted tointermittently engage and advance a film strip having a plurality offilm frames, first cam means adapted to drive said claw to engage andrelease said film strip, second cam means, ratchet means rotatable aboutan axis, pawl means coupled to the second cam means and movable into andout of engagement with said ratchet means for driving said second cammeans synchronously with said first cam means when the pawl means andratchet means are engaged, restraining means operatively coupled to thesecond cam means and positionable relative to the claw by said secondcam means into and out of a position for periOdically holding said clawineffective to engage said film strip, the improvement comprising: meansfor disengaging the pawl means from the ratchet means when the secondcam means has positioned the restraining means in its position forholding the claw ineffective to engage the film strip, thereby effectingprolonged projection of a single frame, said disengaging meanscomprising a catch mounted for movement between (1) a first positionwherein the catch is located with respect to the pawl to disengage thepawl from the ratchet and (2) a second position wherein the catch isdisengaged from the pawl, and said disengaging means further comprisesmeans for moving the catch between its first and second positions.
 2. Ina film transport mechanism having a film claw adapted to engage andadvance a film strip, first cam means adapted to drive said claw toengage and release said film strip, second cam means, ratchet meansrotatable about an axis, pawl means movable into and out of engagementwith said ratchet means for driving said second cam means synchronouslywith said first cam means when the pawl means and ratchet means areengaged, restraining means operatively coupled to the second cam meansand positionable relative to the claw by said second cam means into andout of a position for periodically holding said claw ineffective toengage said film strip, the improvement comprising: disengaging meansshiftable between (1) a first condition wherein said disengaging meansis effective to disengage said pawl from said ratchet means, therebypermitting said restraining means to be held by said second cam means inthe position wherein said claw is ineffective to engage said film stripand (2) a second condition wherein said disengaging means is ineffectiveto disengage said pawl and ratchet means; and a shift means coupled tosaid disengaging means and effective to shift said disengaging meansbetween its first condition and its second condition.
 3. The improvementas set forth in claim 2 further comprising: cycle control meanscontrolled by the second cam and cooperating with said disengaging meansin response to movement of the shift means to effect shifting of thedisengaging means from its first condition to its second condition, saidcycle control means permitting the return of the disengaging means toits first condition from its second condition after advancement of asingle film frame and following movement of the first control means to aposition for moving the disengaging means to its second condition,whereby said film strip is engaged and advanced only one frame each timesaid disengaging means is selectively shifted from its second to itsfirst condition.
 4. For a motion picture projector or the like, atransport mechanism adapted to selectively advance a motion picture filmfor stop frame viewing of a single frame of film, said mechanismcomprising: a. first means for periodically advancing said film at afirst rate, said means comprising a film claw adapted to besynchronously moved into and out of engagement with said film and toadvance said film by a single frame when said film claw is engaged withsaid film; b. second means adapted to periodically restrain said firstmeans from advancing said film, thereby effecting advancement of film ata second rate, said second means comprising cam means operablesynchronously with said film claw and a ratchet and pawl coupled to thecam means for controlling operation of the cam means, the ratchet andpawl being adapted to be shifted between (1) a first condition whereinsaid pawl is disengaged from said ratchet so that said ratchet and pawlare thereby ineffective to operate said cam means; and (2) a secondcondition wherein said pawl is engaged with said ratchet so that saidratchet and pawl are effective to cause said cam means to be operatedsynchronous with said film claw, and restraining means operable by saidcam means for restraining saId film claw from movement into engagementwith said film; c. a member adapted to engage said pawl to change saidratchet and pawl from said second condition to said first condition; andd. means for selectively moving said member between (1) a first positionwherein said member is engageable with said pawl and (2) a secondposition wherein said member is removed a spaced distance from saidpawl.
 5. In a motion picture projector having a film claw adapted toengage and advance a strip of film, first means to drive said claw intoand out of engagement with the film during advancement of an incrementof film, second means adapted to restrain said claw from being driveninto engagement with the film by said first means, said second meansselectively movable between (1) a first position wherein said secondmeans is effective to restrain said claw, and (2) a second positionwherein said second means is ineffective to restrain said claw, theimprovement comprising: a. toggle means movably secured to a firstportion of said projector; b. bracket means movably secured to a secondportion of said projector; c. connecting means for connecting saidtoggle means and said bracket means such that movement of said togglemeans produces movement of said bracket means; d. catch means forselectively cooperating with said second means to move said second meansfrom said first position to said second position, said catch means beinglocated with respect to said bracket means so that the catch means iscontrolled by said bracket means in response to movement of said togglemeans; and e. means for returning said second means from said secondposition to said first position after said claw has engaged and advancedan increment of film.
 6. In a motion picture projector as set forth inclaim 5 wherein said returning means comprises cam means which cooperatewith said bracket means to move said bracket means from (1) a firstposition wherein said bracket is ineffective to cooperate with saidcatch means to (2) a second position wherein said bracket is effectiveto cooperate with said catch means.